We have calculated wide-angle photo- and electroproduction of pions within the handbag factorization
scheme to twist-3 accuracy and LO of perturbative QCD. In this mechanism the amplitudes factorize into
hard partonic subprocess amplitudes and soft form factors representing \(1/x\) -moments of zero-skewness GPDs.
The twist-3 contributions to the subprocess amplitudes include the 2-body, \(q\bar{q}\) , as well as the
3-body, \(q\bar{q}g\) , Fock components of the pion. In light-cone gauge we are using for the vacuum-meson matrix
elements, the equation of motion which is formally an inhomogeneous linear first-order differential equation,
fixes the 2-body twist-3 DAs, \(\phi _{\pi p}\)  and \(\phi _{\pi \sigma }\) , for a given 3-body DA. Thus, only
two independent pion DAs remain as soft physics input to the handbag mechanism in addition to the form
factors, the usual ones, being related to the helicity non-flip GPDs, as well as the transversity form factors.
Taking the DAs and the form factors
from our previous work [1]}, we evaluated the photoproduction cross sections within the handbag
mechanism and compared the results with experimental data. It seems that the energy dependence of the
handbag contribution is somewhat too strong. Including evolution and the \(t\) -dependence of the form factors
it is approximately \(s^{-9}\)  at fixed \(\cos {\theta }\) . Therefore, as an alternative we also presented results
evaluated at the fixed scale of \(1\,\,{\rm GeV}\)  which agree fairly well with experiment. A better determination of
the large \(-t\)  behavior of the form factors is required before a final answer can be given what the energy
dependence of handbag predictions is. We also give detailed predictions for pion electroproduction and discuss
spin effects, especially helicity correlations. The gross features of wide-angle electroproduction bear
similarities to DVMP: the \(\pi ^0\)  channel is dominated by the twist-3 contributions, for the \(\pi ^\pm \) 
channels twist-2 contributions matter in the forward hemisphere. Data on pion electroproduction would
allow to extract detailed information on the large \(-t\) -behavior of the form factors and the transversity
GPDs at zero skewness. This knowledge bears implications of our understanding of the parton densities in the
transverse position plane [2]}, [3]}. It may also be of help in understanding some of the
spin density matrix elements of deeply virtual vector-meson production [4]}, [5]}.
In the present work, we restricted ourselves to the case of the pion. However, the generalization to other
pseudoscalar mesons is straightforward.
